Measuring interdisciplinarity of a research system: detecting distinction between publication categories and citation categories

Interdisciplinary research has been a focus in academia, and it is beneficial to understand the properties and structure of interdisciplinary research from the viewpoint of bibliometrics. This paper detects distinctions between publication categories and citation categories to measure the interdisciplinarity of individual publications, and then to measure interdisciplinarity for one research system by the average interdisciplinarity of individual publications, which are taken as elements in the research system. The average and the standard deviation (SD) that reflects the variance of the elements’ interdisciplinarity in one research system, of all the publications’ integration scores and diffusion scores, were then respectively calculated. Sixty of the most productive authors from three Web of Science categories (Mathematics, Applied; Computer Science, Artificial Intelligence; and Operations Research and Management Science) were selected as a case to validate our approach. The results showed that measuring the interdisciplinarity of individual elements effectively lessened the impacts caused by some elements with distinctive citation categories on the research system’s interdisciplinarity (especially those research systems with large SDs). Furthermore, measuring the distinction between publication categories and citation categories is essential for individual publications’ interdisciplinarity when the citation categories do not appear in the categories of the publication itself or the publication has only a single citation category.